1. Field of the Invention
The present invention concerns methods and devices to execute commands in components of an imaging system, and an imaging system, in particular a magnetic resonance tomography apparatus.
2. Description of the Prior Art
Magnetic resonance tomography apparatuses are known from DE 10 2005 052 564, for example.
Modern magnetic resonance systems operate with coils to emit radio-frequency pulses for nuclear magnetic resonance excitation and to receive induced magnetic resonance signals. A magnetic resonance system typically has a permanent magnet or a superconducting coil to generate a basic magnetic field (H0) that is optimally homogeneous in an examination region, a large coil known as a whole-body coil, (also called a body coil or BC) that is normally permanently installed in the MR apparatus, and multiple small local coils (also called surface coils or LCs). To obtain information from which images of a patient can be generated, selected regions of the subject to or, respectively, patient be examined are read out with independently controllable, magnetically orthogonal gradient coils for three axes (for example X, Y approximately radial to the patient, Z in the longitudinal direction of the patient).
Spatially separate components of a magnetic tomography system conventionally have been connected via a number of dedicated control signals (for example “RF_ON”) via optical waveguide connections, for example. These control signals are defined based on a central system clock of a central controller (for example 10 MHz). When these control signals are generated or decoded in clock domains that are faster than this system clock, a rigid relationship with the system clock is established by synchronization.
Due to a spatial separation and a simplified scaling capability of the components, it is complicated to conduct the multiple control signals in a base system that are required for the maximum expansion. A new structure of an MR with an optical PCI express bus has been considered. However, the problem arises that now the data and commands to the components controlled via the PCI Express bus arrive at different and variable times. Commands should be executed with extreme precision. The revolution of a spin (360°) in a 3T system is ( 1/123 MHz=) 8 ns. However, the required phase lock characteristic of the commands must be significantly better so that the same phase conditions (between transmission system and reception system) can be reproducibly achieved.